Localization of PD-events in HV-Windings of Rotating Machines

Rotating electrical machines are a vital component in the power generation as well as in the industrial production. Unexpected failures in such assets can lead to high follow up costs, caused by the machine itself and the resulting down times. A reliable PD diagnosis is a powerful tool to find potential weak spots in the winding insulation system and to prevent such unexpected outages. As an interpretation and risk assessment tool, the phase resolved pattern (PRPD) is well established and accepted. The shape of the PD pattern allows to identify the type of the fault. However, so far, no system is available, which can correlate the fault directly with the location within the winding. This paper presents the key results of comprehensive investigations and the development of an algorithm which targets the partial discharge localization in spatial distributed rotating machine windings. Limitations and accuracy of the developed tool are discussed using different rotating machine windings. Artificial and real partial discharge events which have been provoked at various positions along the insulation system could be localized reliably within certain limits. With the presented method a correlation is obtained between the phase resolved pattern and the position of the PD source along the winding. The knowledge of the position along coil allows the test engineer to judge if the localized PD source is active in normal operation, without dismantling the machine. The localization approach is based on the measurement of the electrical impulses. Therefore, possible PD sources can be localized even though they might not be detectable during a visual inspection, enabling a selective repair.